The disclosure relates generally to supporting cooperative transmission in a massive multiple-input multiple-output (MIMO) system, such as a wireless distribution system (WDS).
Wireless customers are increasingly demanding digital data services, such as streaming video signals. At the same time, some wireless customers use their wireless communications devices in areas that are poorly serviced by conventional cellular networks, such as inside certain buildings or areas where there is little cellular coverage. One response to the intersection of these two concerns has been the use of DASs. DASs include remote units configured to receive and transmit communications signals to client devices within an antenna range of the remote units. DASs can be particularly useful when deployed inside buildings or other indoor environments where the wireless communications devices may not otherwise be able to effectively receive RF signals from a source.
In this regard, FIG. 1 illustrates a distribution of communications services to coverage cells 100(1)-100(N) of a WDS provided in the form of a DAS 102, wherein ‘N’ is the number of coverage cells. These communications services can include cellular services, wireless services, such RF identification (RFID) tracking, Wireless Fidelity (Wi-Fi), local area network (LAN), and wireless LAN (WLAN), wireless solutions (Bluetooth, Wi-Fi Global Positioning System (GPS), signal-based, and others) for location-based services, and combinations thereof, as examples. The coverage cells 100(1)-100(N) may be remotely located. In this regard, the coverage cells 100(1)-100(N) are created by and centered on remote units 104(1)-104(N) connected to a central unit 106 (e.g., a head-end equipment, a head-end controller, or a head-end unit). The central unit 106 may be communicatively coupled to a signal source 108, for example, a base transceiver station (BTS) or a baseband unit (BBU). In this regard, the central unit 106 receives downlink communications signals 110D from the signal source 108 to be distributed to the remote units 104(1)-104(N). The remote units 104(1)-104(N) are configured to receive the downlink communications signals 110D from the central unit 106 over a communications medium 112 to be distributed to the respective coverage cells 100(1)-100(N) of the remote units 104(1)-104(N). Each of the remote units 104(1)-104(N) may include an RF transmitter/receiver and a respective antenna 114(1)-114(N) operably connected to the RF transmitter/receiver to wirelessly distribute the communications services to client devices 116 within the respective coverage cells 100(1)-100(N). The remote units 104(1)-104(N) are also configured to receive uplink communications signals 110U from the client devices 116 in the respective coverage cells 100(1)-100(N) to be distributed to the signal source 108. The size of each of the coverage cells 100(1)-100(N) is determined by the amount of RF power transmitted by the respective remote units 104(1)-104(N), receiver sensitivity, antenna gain, and RF environment, as well as by RF transmitter/receiver sensitivity of the client devices 116. The client devices 116 usually have a fixed maximum RF receiver sensitivity, so that the above-mentioned properties of the remote units 104(1)-104(N) mainly determine the size of the respective coverage cells 100(1)-100(N).
The DAS 102 and the coverage cells 100(1)-100(N) can be configured to function as a massive MIMO system, in which the coverage cells 100(1)-100(N) each form a respective micro coverage cell. The remote units 104(1)-104(N) in the coverage cells 100(1)-100(N) may be provided as low-power remote radio heads (RRHs) to distribute the downlink communications signals 110D and/or receive the uplink communications signals 110U using the same RF spectrum (e.g., RF band/channel). In this regard, it may be possible to adapt the DAS 102 to support the next generation (e.g., fifth-generation (5G)) wireless communications systems.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.